Interference cancellation relay device

ABSTRACT

Provided is an interference cancellation relay device. The interference cancellation relay device includes: an interference cancellation unit cancelling an interference signal from an input signal and outputting the input signal from which the interference signal is removed; a gain control unit controlling a gain of an output signal of the interference cancellation unit; and a pre-distortion unit distorting the output signal of the interference cancellation unit, of which the gain is controlled by the gain control unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/117,926, filed Aug. 10, 2016 which is a National Stage ofInternational Application No. PCT/KR2014/005900, filed Jul. 2, 2014, andclaims priority from Korean Patent Applications No. 10-2014-0037347filed Mar. 29, 2014, the contents of which are incorporated herein byreference in their entireties.

BACKGROUND 1. Field

The inventive concept relates to an interference cancellation relaydevice, and particularly, to an interference cancellation relay devicehaving a pre-distortion function.

2. Description of Related Art

In general, a relay device is used for transmitting a signal between abase station and a terminal and extension of a service or improvement ofa service quality in a radio signal shadow area. A wireless relay devicemay be provided as one example of the relay device, and the wirelessrelay device provides a communication service for receiving the signaltransmitted from the base station or the terminal through a receivingantenna, amplifying the received signal, and transmitting the amplifiedsignal to the terminal or the base station through a transmittingantenna.

In the case of the wireless relay device, a degree of isolation at apredetermined level or higher is required between the receiving antennaand the transmitting antenna in order to prevent deterioration inquality of the communication service. In recent years, as it has beendifficult to secure the degree of isolation due to a spatial limitationaccording to a miniaturization demand trend of the wireless relaydevice, a research into an interference cancellation relay device hasbeen actively conducted, which can secure the degree of isolation whileovercoming the spatial limitation by applying an interferencecancellation function to cancel feed-back signals, that is, signalsinput into the receiving antenna as interference signals through avariety of paths, after the signals are radiated from the transmittingantenna.

In addition, the radio relay device has a power amplifier at atransmitting end to transmit a signal having sufficient power to theterminal or the base station and the deterioration in quality of thecommunication service is caused due to a non-linear characteristic ofthe power amplifier. For preventing the quality deterioration, anattempt for implementing a pre-distortion function for improving thenon-linear characteristic of the power amplifier in the wireless relaydevice has been continued and in particular, an attempt for implementingthe pre-distortion function even in the interference cancellation relaydevice has been actively made.

However, in the case of the interference cancellation relay device,since the received signal significantly fluctuates due to theinterference signals, it is difficult to implement the pre-distortionfunction therein.

SUMMARY

The inventive concept directs to an interference cancellation relaydevice in which a pre-distortion function can be stably implemented.

According to an aspect of the inventive concept, there is provided aninterference cancellation relay device, comprising: an interferencecancellation unit cancelling an interference signal from an input signaland outputting the input signal from which the interference signal iscancelled; a gain control unit controlling a gain of an output signal ofthe interference cancellation unit; and a pre-distortion unit distortingthe output signal of the interference cancellation unit, of which thegain is controlled by the gain control unit.

According to an exemplary embodiment, wherein the gain control unit mayinclude, a measurement unit detecting a reference signal from the outputsignal of the interference cancellation unit and measuring an intensityof the reference signal; and a control unit controlling the gain of theoutput signal of the interference cancellation unit by using theintensity of the reference signal.

According to an exemplary embodiment, wherein the reference signal maybe a signal having a predetermined intensity regardless of fluctuationof a data amount included in the input signal.

According to an exemplary embodiment, wherein the measurement unit mayinclude, a detection unit detecting the reference signal from the outputsignal of the interference cancellation unit; and a calculation unitcalculating the intensity of the reference signal.

According to an exemplary embodiment, wherein the control unit mayinclude, a comparison unit comparing the intensity of the referencesignal with a predetermined reference intensity; and a control unitcontrolling the gain of the output signal of the interferencecancellation unit according to a result of comparing the intensity ofthe reference signal and the reference intensity.

According to another aspect of the inventive concept, there is providedan interference cancellation relay device, comprising: a first gaincontrol unit controlling a gain of an input signal; a conversion unitdigitalizing the input signal of which the gain is controlled by thefirst gain control unit; an interference cancellation unit cancelling aninterference signal from the digitalized input signal and outputting theinput signal from which the interference signal is cancelled; a secondgain control unit controlling the gain of the output signal of theinterference cancellation unit; and a pre-distortion unit distorting theoutput signal of the interference cancellation unit, of which the gainis controlled by the second gain control unit.

According to an exemplary embodiment, wherein the second gain controlunit may include, a measurement unit detecting a reference signal fromthe output signal of the interference cancellation unit and measuring anintensity of the reference signal; and a first control unit controllingthe gain of the output signal of the interference cancellation unit byusing the intensity of the reference signal.

According to an exemplary embodiment, wherein the reference signal maybe a signal having a predetermined intensity regardless of fluctuationof a data amount included in the input signal.

According to an exemplary embodiment, wherein the first gain controlunit may control the gain of the input signal by using the intensity ofthe reference signal, which is measured by the measurement unit.

According to an aspect of the inventive concept, an interferencecancellation relay device includes a gain control unit constantlycontrolling an output signal of an interference cancellation unit andproviding the output signal to a pre-distortion unit, and as a result,the interference of signals and the oscillation can be minimized and thepre-distortion unit can stably improve a non-linear characteristic of apower amplifier, thereby improving the quality of a communicationservice.

BRIEF DESCRIPTION OF THE FIGURES

A brief description of each drawing is provided to more sufficientlyunderstand drawings used in the detailed description of the inventiveconcept.

FIG. 1 is a diagram for describing a relay environment of aninterference cancellation relay device according to an embodiment of theinventive concept.

FIG. 2 is a block diagram schematically illustrating an interferencecancellation relay device according to an embodiment of the inventiveconcept.

FIGS. 3 and 4 are diagrams for, in detail, describing some components ofthe interference cancellation relay device of FIG. 2.

FIG. 5 is a block diagram schematically illustrating an interferencecancellation relay device according to another embodiment of theinventive concept.

FIGS. 6 and 7 are diagrams for, in detail, describing some components ofthe interference cancellation relay device of FIG. 5.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The inventive concept may be variously modified and have variousembodiments, so that specific embodiments will be illustrated in thedrawings and described in the detailed description. However, this doesnot limit the inventive concept to specific embodiments, and it shouldbe understood that the inventive concept covers all the modifications,equivalents and replacements included within the idea and technicalscope of the inventive concept.

In describing the inventive concept, in the following description, adetailed explanation of known related technologies may be omitted toavoid unnecessarily obscuring the subject matter of the inventiveconcept. In addition, numeral figures (for example, 1, 2, and the like)used during describing the specification just are identification symbolsfor distinguishing one element from another element.

Further, in the specification, if it is described that one component is“connected” or “accesses” the other component, it is understood that theone component may be directly connected to or may directly access theother component but unless explicitly described to the contrary, anothercomponent may be “connected” or “access” between the components.

Further, terms including “unit”, “er”, “member”, “module”, and the likedisclosed in the specification mean a unit that processes at least onefunction or operation and this may be implemented by hardware orsoftware or a combination of hardware and software.

In addition, it will be apparent that in the specification, componentsare just classified for each main function which each component takescharge of. That is, two or more components to be described below may beprovided to be combined into one component or one component may beprovided to be separated into two or more for each of more subdividedfunctions. In addition, each of the components to be described below mayadditionally perform some or all functions among functions which othercomponents take charge of in addition to the main function which eachcomponent takes charge of and some functions among the main functionswhich the respective take charge of may be exclusively charged andperformed by other components.

Hereinafter, embodiments of the inventive concept will be sequentiallydescribed in detail.

FIG. 1 is a diagram for describing a relay environment of aninterference cancellation relay device 10 according to an embodiment ofthe inventive concept. In FIG. 1, a donor antenna transceiving a signalwith a base station BTS is illustrated as a receiving antenna RX and aservice antenna transceiving the signal with a terminal MS isillustrated as a transmitting antenna TX, for convenience of theexplanation. In addition, in FIG. 1, it is illustrated that theinterference cancellation relay device 10 includes one receiving antennaRX and one transmitting antenna TX, but is not limited thereto andinterference cancellation relay device 10 may include at least tworeceiving antennas RX and at least two transmitting antennas TX.

Referring to FIG. 1, the interference cancellation relay device 10 mayamplify a downlink signal of the base station BTS received through thereceiving antenna RX and transmit the amplified downlink signal to theterminal MS through the transmitting antenna TX.

In this case, signals radiated through the transmitting antenna TX areinput into the receiving antenna RX through wireless environment to forminterference signals. As a result, while the downlink signal of the basestation BTS, which is an original signal input into the receivingantenna RX and the interference signals are aggregated to be amplified,the interference cancellation relay device 10 may be oscillated. Inorder to solve the oscillation problem, the interference cancellationrelay device 10 includes an interference cancellation unit 300 (see FIG.2 or 5) that may cancel interference signals caused by the signalradiated from the transmitting antenna TX from the downlink signal ofthe base station BTS.

In addition, when the interference cancellation relay device 10amplifies the downlink signal of the base station BTS through the poweramplifier (not illustrated) and transmits the amplified downlink signal,the downlink signal of the base station BTS is distorted due to thenon-linear characteristic of the power amplifier, and as a result, thequality of a communication service may deteriorate. In order to solvethe quality deterioration, the interference cancellation relay device 10includes a pre-distortion unit 500 (see FIG. 2 or 5) that pre-distortsan input signal into the amplifier based on the non-linearcharacteristic of the power amplifier, which is measured by detecting anoutput signal of the power amplifier.

As a general interference cancellation relay device receives thedownlink signal of the base station through wirelessly, that is, throughthe receiving antenna as described above, the general interferencecancellation relay device is influenced by the interference signals, andas a result, an input signal into the interference cancellation relaydevice is rapidly changed. Thus, in the general interferencecancellation relay device, it is difficult to stably perform thepre-distortion function and it is difficult to secure qualityreliability of the communication service.

On the contrary, the interference cancellation relay device 10 accordingto the inventive concept includes a gain control unit 400 (see FIG. 2 or5 that constantly maintains an output signal gain of the interferencecancellation unit to allow the pre-distortion unit to stably operate,thereby securing the reliability of the communication service.Hereinafter, this will be described in detail with reference to FIG. 2,and the like.

Meanwhile, the interference cancellation relay device 10 may amplify anuplink signal of the terminal MS, which is received through thetransmitting antenna TX and transmit the amplified uplink signal to thebase station BTS through the receiving antenna RX. Although notillustrated in FIG. 1, even in this case, signals radiated through thereceiving antenna RX are input into the transmitting antenna TX throughthe wireless environment to form the interference signal, and as aresult, as the uplink signal of the terminal MS, which is an originalsignal input into the transmitting antenna TX and the interferencesignal are aggregated and amplified, the interference cancellation relaydevice 10 may be oscillated. Although not illustrated in FIG. 1, theinterference cancellation relay device 10 may further include aninterference cancellation unit, a gain control unit, and apre-distortion unit in an uplink similarly to the interferencecancellation unit, the gain control unit, and the pre-distortion unit inthe downlink. In this case, components which correspond to each other inthe downlink and the uplink of the interference cancellation relaydevice 10 may be implemented as one or implemented separately. Forexample, the gain control unit in the downlink and the gain control unitin the uplink of the interference cancellation relay device 10 may beimplemented as one component or implemented as respective distinguishedcomponents.

FIG. 2 is a block diagram schematically illustrating an interferencecancellation relay device 10 according to an embodiment of the inventiveconcept. In FIG. 2, only components for transmitting the downlink signalof the base station BTS (see FIG. 1) to the terminal MS (see FIG. 1) inthe interference cancellation relay device 10 are illustrated forconvenience of the explanation. Since components for transmitting theuplink signal of the terminal MS (see FIG. 1) to the base station BTS(see FIG. 1) may correspond to the components for transmitting thedownlink signal, hereinafter, detailed description of the components fortransmitting the uplink signal will be omitted. Further, a receptionprocessing unit 100 and an analog/digital conversion unit 200 and adigital/analog conversion unit 600 and a transmission processing unit700 are illustrated as respective separate components for convenience ofthe explanation in FIG. 2.

Referring to FIG. 2, the interference cancellation relay device 10 mayinclude the receiving antenna RX, the reception processing unit 100, theanalog/digital conversion unit 200, the interference cancellation unit300, the gain control unit 400, the pre-distortion unit 500, thedigital/analog conversion unit 600, the transmission processing unit700, and the receiving antenna TX.

The reception processing unit 100 may receive an input signal providedto the interference cancellation relay device 10 from the base stationBTS (see FIG. 1) through the receiving antenna RX. The input signal mayinclude at least one of the downlink signal of the base station BTS (seeFIG. 1) and the interference signal based on the signal radiated throughthe transmitting antenna TX.

The reception processing unit 100 may be configured to eliminate noisefrom the input signal and frequency-down-convert the input signal andoutput the input signal which is frequency-down-converted. For example,the reception processing unit 100 may include a filter for selecting arequired band in the input signal, a low noise amplifier amplifying theinput signal by minimizing the noise in the input signal, and afrequency down converter converting the input signal amplified by thelow noise amplifier into a signal in an intermediate frequency band froma signal in a radio frequency (RF) band, and perform signal processingfor converting the input signal into a digital signal by theanalog/digital conversion unit 200 through the above-describedcomponents. Herein, the frequency down converter may be optionallyomitted.

The reception processing unit 100 may further include a filter foreliminating an image frequency from the input signal between the lownoise amplifier and the frequency down converter. Further, the receptionprocessing unit 100 may further include the amplifier for amplifying theinput signal converted into the signal in the intermediate frequencyband, another frequency down converter for converting the amplifiedinput signal in the intermediate frequency band into a signal in abaseband, and the like.

The analog/digital conversion unit 200 may receive the input signalsignal-processed by the reception processing unit 100. Theanalog/digital conversion unit 200 may convert the input signalsignal-processed by the reception processing unit 100 into the digitalsignal.

The interference cancellation unit 300 may receive the input signaldigitalized from the analog/digital conversion unit 200. Theinterference cancellation unit 300 may cancel the interference signalfrom the digitalized input signal and output the digitalized inputsignal from which the interference signal is cancelled. For example, theinterference cancellation unit 300 may model an estimation interferencesignal corresponding to the interference signal based on the digitalizedinput signal input into the interference cancellation unit 300 or theoutput signal of the interference cancellation unit 300, which is fedback, and cancel the interference signal from the digitalized input byusing the modeled estimation interference signal and output the downlinksignal which is the original signal.

The gain control unit 400 may control a gain of the output signal of theinterference cancellation unit 300, that is, the digitalized inputsignal from which the interference signal is canceled. The gain controlunit 400 may constantly maintain the gain of the output signal of theinterference cancellation unit 300 to correspond to a predeterminedlevel. Hereinafter, this will be described in more detail with referenceto FIGS. 3 and 4.

The pre-distortion unit 500 may receive the output signal of theinterference cancellation unit 300, of which the gain is controlled bythe gain control unit 400. The pre-distortion unit 500 may distort andoutput the output signal of the interference cancellation unit 300, ofwhich the gain is controlled by the gain control unit 400 based on thenon-linear characteristic of a power amplifier (not illustrated)included in the transmission processing unit 700. For example, thepre-distortion unit 500 may receive the output signal of the poweramplifier, measure the non-linear characteristic of the power amplifierfrom the output signal of the power amplifier, and distort and outputthe output signal of the interference cancellation unit 300, of whichthe gain is controlled so as to have non-linearity contrary to themeasured non-linear characteristic of the power amplifier.

The digital/analog conversion unit 600 may receive the output signal ofthe interference cancellation unit 300, which is distorted by thepre-distortion unit 500. The digital/analog conversion unit 600 mayconvert the output signal of the interference cancellation unit 300 intothe analog signal.

The transmission processing unit 700 may be configured tofrequency-up-convert, amplify, and output the analog signal. Forexample, the transmission processing unit 700 may include a frequency upconverter up-converting the analog signal into the signal in the radiofrequency band, a power amplifier amplifying and outputting the signalfrequency-up-converted by the frequency up converter, and a filter forselecting a band required in the amplified signal, and perform signalprocessing for transmitting the analog signal to the terminal MS (seeFIG. 1) through the transmitting antenna TX by using the aforementionedcomponents. Herein, the frequency up converter may be optionallyomitted.

The transmission processing unit 700 may further include an isolator forprotecting the power amplifier, and the like at the rear end of thepower amplifier.

As described above, the interference cancellation relay device 10includes the gain control unit 400 between the interference cancellationunit 300 and the pre-distortion unit 500 to constantly maintain the gainof the signal input into the pre-distortion unit 500, and therebypreventing distortion of a transmission signal while minimizinginterference and oscillation of the signal by the interferencecancellation unit 300, and as a result, the quality of the communicationservice may be enhanced.

FIGS. 3 and 4 are diagrams for, in detail, describing some components ofthe interference cancellation relay device 10 of FIG. 2. FIG. 3 is adiagram illustrating, in more detail, a gain control unit 400 and FIG. 4is a diagram illustrating one implementation example of a measurementunit 420 and a control unit 440 in the gain control unit 400.

Referring to FIGS. 3 and 4, the gain control unit 400 may include themeasurement unit 420 and the control unit 440.

The measurement unit 420 may detect a reference signal from the outputsignal of the interference cancellation unit 300 that is the digitalizedinput signal, which is corresponded to the downlink signal equivalent tothe original signal according as the interference signal is cancelledtherefrom, and measure the intensity of the reference signal. Thereference signal may be a signal having a predetermined intensityregardless of fluctuation of a data amount included in the downlinksignal provided from the base station BTS (see FIG. 1) among inputsignals into the interference cancellation relay device 10. For example,when a mobile communication service provided by the interferencecancellation relay device 10 is long term evolution (LTE), the referencesignal may be a primary synchronization signal (PSS) or a secondarysynchronization signal (SSS) which is a signal distinguished from a datasignal and is a synchronization signal. Alternatively, when the mobilecommunication service provided by the interference cancellation relaydevice 10 is wideband code division multiple access (WCDMA)/CDMA, thereference signal may be a pilot signal which is a synchronizationsignal.

The measurement unit 420 may include a detection unit 422 detecting thereference signal from the output signal of the interference cancellationunit 300 and a calculation unit 424 calculating the intensity of thedetected reference signal. For example, when the reference signal is theprimary synchronization signal, the detection unit 422 may filter theprimary synchronization signal which is present at a center frequency inthe output signal of the interference cancellation unit 300 and thecalculation unit 424 may be configured to calculate the intensity of thefiltered primary synchronization signal.

The control unit 440 may control the gain of the output signal of theinterference cancellation unit 300 by using the intensity of thereference signal measured by the measurement unit 420. For example, thecontrol unit 440 compares the intensity of the reference signal with apredetermined reference intensity and control the gain of the outputsignal of the interference cancellation unit 300 according to a resultof the comparison. The predetermined reference intensity may correspondto a level of the gain to allow the pre-distortion unit 500 to stablyoperate. The reference intensity may be provided from a processor (notillustrated) of the interference cancellation relay device 10 andupdated adaptively to a change of the communication service, and thelike.

The control unit 440 may include a comparison unit 442 comparing theintensity of the reference signal with the predetermined referenceintensity and a an adjustment unit 444 controlling the gain of theoutput signal of the interference cancellation unit 300 according to aresult of the comparison. For example, according to the comparisonresult by the comparison unit 442, when the intensity of the referencesignal is larger than the reference intensity, the adjustment unit 444may decrease the gain of the output signal of the interferencecancellation unit 300, when the intensity of the reference signal issmaller than the reference intensity, the adjustment unit 444 mayincrease the gain of the output signal of the interference cancellationunit 300, and when intensity of the reference signal is the same as thereference intensity, the adjustment unit 444 may be configured tomaintain the gain of the output signal of the interference cancellationunit 300.

FIG. 5 is a block diagram schematically illustrating an interferencecancellation relay device 10′ according to another embodiment of theinventive concept. The interference cancellation relay device 10′illustrated in FIG. 5 as a modified example of the interferencecancellation relay device 10 illustrated in FIG. 2 further includes ananalog gain control unit 800 between the reception processing unit 100and the analog/digital conversion unit 200 unlike the interferencecancellation relay device 10 of FIG. 2. In describing FIG. 5, duplicateddescription with FIGS. 2 to 4 will be omitted and a different from FIGS.2 to 4 will be primarily described.

Referring to FIG. 5, the interference cancellation relay device 10′ mayinclude the receiving antenna RX, the reception processing unit 100, theanalog gain control unit 800, the analog/digital conversion unit 200,the interference cancellation unit 300, the gain control unit(hereinafter, referred to as a digital gain control unit for convenienceof the explanation, 400), the pre-distortion unit 500, thedigital/analog conversion unit 600, the transmission processing unit700, and the receiving antenna TX.

The reception processing unit 100 may receive the input signal providedto the interference cancellation relay device 10 from the base stationBTS (see FIG. 1) through the receiving antenna RX and may be configuredto eliminate the noise from the input signal and down-convert thefrequency of the input signal and output the input signal.

The analog gain control unit 800 may control the gain of the inputsignal signal-processed by the reception processing unit 100. The analoggain control unit 800 may constantly maintain the gain of the inputsignal signal-processed by the reception processing unit 100 tocorrespond to a predetermined level.

Meanwhile, it is illustrated that the analog gain control unit 800 is acomponent apart from the reception processing unit 100 for convenienceof the explanation, but the inventive concept is not limited thereto.The analog gain control unit 800 may be included in the receptionprocessing unit 100, of course.

The analog/digital conversion unit 200 may receive the input signal ofwhich the gain is controlled by the analog gain control unit 800 andconvert the received input signal into the digital signal.

The interference cancellation unit 300 may receive the input signaldigitalized from the analog/digital conversion unit 200 and cancel theinterference signal from the digitalized input signal and output theinput signal from which the interference signal is cancelled.

The digital gain control unit 400 may control the gain of the outputsignal of the interference cancellation unit 300, that is, thedigitalized input signal from which the interference signal iscancelled. The gain control unit 400 may constantly maintain the gain ofthe output signal of the interference cancellation unit 300 tocorrespond to a predetermined level.

The pre-distortion unit 500 may receive the output signal of theinterference cancellation unit 300 of which the gain is controlled bythe digital gain control unit 400 and distort and output the outputsignal of the interference cancellation unit 300 based on the non-linearcharacteristic of the power amplifier (not illustrated) included in thetransmission processing unit 700.

The digital/analog conversion unit 600 may receive the output signal ofthe interference cancellation unit 300, which is distorted by thepre-distortion unit 500 and convert the output signal into the analogsignal.

The transmission processing unit 700 may be configured tofrequency-up-convert and amplify the analog signal and transmit thecorresponding signal to the terminal MS (see FIG. 1) through thetransmitting antenna TX.

As described above, the interference cancellation relay device 10′includes the digital gain control unit 400 between the interferencecancellation unit 300 and the pre-distortion unit 500 to constantlymaintain the gain of the signal input into the pre-distortion unit 500and constantly maintain the gain of the signal input into theinterference cancellation unit 300 after digitally converted, therebypreventing oscillation and distortion of transmission signals, and as aresult, the quality of the communication service may be improved.

FIGS. 6 and 7 are diagrams for, in detail, describing some components ofthe interference cancellation relay device 10′ of FIG. 5. FIG. 6 is adiagram illustrating, in more detail, a digital gain control unit 400and an analog gain control unit 800 and FIG. 7 is a diagram illustratingone implementation example of a connection between a measurement unit420 and a digital control unit 440 and between an analog gain controlunit 800 and a measurement unit 420 in the digital gain control unit400. In describing FIGS. 6 and 7, duplicated description with FIGS. 2 to4 will be omitted and a different from FIGS. 2 to 4 will be primarilydescribed.

Referring to FIGS. 6 and 7, the digital control unit 440 of the digitalgain control unit 400 may constantly maintain the gain of the outputsignal of the interference cancellation unit 300 by using the intensityof the reference signal, which is measured by the measurement unit 420,for example, an intensity of a signal having a predetermined intensityregardless of fluctuation of the data mount included in the downlinksignal provided from the base station BTS (see FIG. 1) among inputsignals into the interference cancellation relay device 10′.

The analog gain control unit 800 may constantly maintain the gain of theinput signal digitalized through the analog/digital conversion unit 200and input into the interference cancellation unit 300 by using theintensity of the reference signal, which is measured by the measurementunit 420 of the digital gain control unit 400. In some embodiments, theanalog gain control unit 800 may be configured similarly to the digitalcontrol unit 440 of the digital gain control unit 400.

Hereinabove, the inventive concept has been described in detail withreference to a preferred embodiment, but the inventive concept is notlimited to the embodiment and various modifications and changes can bemade by those skilled in the art within the technical spirit and scopeof the inventive concept.

What is claimed is:
 1. A gain control device, comprising at least oneprocessor and at least one memory to implement: a measurement unitextracting a reference signal from a target signal and measuring anintensity of the reference signal, wherein the reference signal ispredefined as control data to control receipt of user data and isdistinct from the user data; and a control unit controlling a gain ofthe target signal according to a result of comparison between theintensity of the reference signal and a predetermined referenceintensity, wherein the predetermined reference intensity is updateableadaptively to a change of a communication service regarding the targetsignal.
 2. The gain control device of claim 1, wherein the control unitincludes: a comparison unit comparing the intensity of the referencesignal with the predetermined reference intensity; and an adjustmentunit adjusting the gain of the target signal based on the result of thecomparison.
 3. The gain control device of claim 1, wherein the referencesignal is a signal having a predetermined intensity regardless offluctuation of a data amount included in the target signal.
 4. The gaincontrol device of claim 1, wherein the measurement unit includes: anextraction unit extracting the reference signal from the target signal;and a calculation unit calculating the intensity of the referencesignal.
 5. The gain control device of claim 1, further comprising: aninterference cancellation unit cancelling an interference signal fromthe target signal and outputting the interference canceled-targetsignal.
 6. The gain control device of claim 5, wherein the control unitfurther controls a gain of the interference canceled-target signal. 7.The gain control device of claim 6, wherein the at least one processorand the at least one memory further implement: a pre-distortion unitdistorting the interference canceled-target signal after the controlledgain is applied.
 8. A method of controlling a gain by a control device,comprising: extracting a reference signal from a target signal, whereinthe reference signal is predefined as control data to control receipt ofuser data and is distinct from the user data; measuring an intensity ofthe reference signal; and comparing the intensity of the referencesignal with a predetermined reference intensity; and adjusting the gainof the target signal based on a result of the comparing, wherein thepredetermined reference intensity is updatable adaptively to a change ofa communication service regarding the target signal.
 9. The method ofclaim 8, wherein the reference signal is a signal having a predeterminedintensity regardless of fluctuation of a data amount included in thetarget signal.
 10. The method of claim 8, wherein the measuring theintensity of the reference signal comprises: extracting the referencesignal from the target signal; and calculating the intensity of thereference signal.
 11. The method of claim 8, further comprising:cancelling an interference signal from the target signal; and outputtingthe interference canceled-target signal.
 12. The method of claim 11,further comprising: controlling a gain of the interferencecanceled-target signal.
 13. The method of claim 12, further comprising:distorting the interference canceled-target signal after the controlledgain is applied.